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significantly higher normal stresses compared to that associated with the sideslope liner <br />system stability analysis discussed previously. <br />A shear -reinforced GCL and a double -sided texture HDPE geomembrane should be used <br />in both the base and the side slope liner systems. Based on our past experience, a <br />residual shear strength envelope defined by a friction angle of 11-12 degrees is <br />considered achievable for the textured HDPE geomembrane-GCL interface and the <br />internal shear strength of the GCL. A similar residual shear strength is considered <br />achievable with the geocomposite drain -textured HDPE geomembrane interface. <br />Therefore, a residual shear strength envelope defined by a friction angle of 11-12 degrees <br />was considered achievable within both the base and sideslope liner systems, over the <br />normal stress range of interest of 0-12000 psf. <br />3.5.4 Results of the Analysis <br />For slope stability cross-sections AA, BB, and CC, iterative slope stability analyses were <br />performed to determine the minimum shear strength required within the liner systems <br />(base and sideslope) to achieve the minimum acceptable factor of safety of 1.5. The <br />results of slope stability analysis for static conditions for all three cross-sections are <br />included in Attachment 1. The results are discussed below. <br />Cross -Section AA <br />is The slope stability analysis was performed assuming waste sideslopes of 314:1 V with <br />three 20 -foot wide horizontal benches. The benches are assumed to be at elevations 300, <br />350, and 400 feet. The analysis shows that the liner systems should meet a minimum <br />residual shear strength envelope defined by a friction angle of 10.5 degrees. Since this <br />friction value is less than 11 degrees, it is considered achievable. <br />Cross -Section BB <br />The initial analysis was performed assuming waste slopes of 3H:1 V with three 20 -foot <br />wide horizontal benches, one each at elevations 300, 350, and 400 feet. This analysis <br />shows that the liner systems should meet a minimum residual shear strength envelope <br />defined by a friction angle of greater than 11.5 degrees. Because the friction angle <br />requirement is close to 12 degrees, the analysis was revised by restricting the maximum <br />waste slopes to 3.5H:1 V. The revised analysis reduces the friction angle requirement to <br />10.5 degrees, which is less than 11 degrees. <br />Cross -Section CC <br />The initial analysis was performed assuming waste slopes of 3H:1 V with three 20 -foot <br />wide horizontal benches, one each at elevations 300, 350, and 400 feet. This analysis <br />shows that the liner systems should meet a minimum residual shear strength envelope <br />( \\.SACRFPI\COMMON\sacDP\2002\PRJ\PJ8\83\835608.2bz.doc EMCOWOWT, Inc. <br />Rev. 0, 07/31/02 <br />3-5 <br />